Engine electrical generator cooling device and method

ABSTRACT

A rotor for an electrical generator is disclosed, including a rotor body having a circular portion and a cylindrical portion coaxial with the circular portion. A generally cylindrical recess is defined by the cylindrical portion and the first side of the circular portion for receiving a stator. At least one first wall is at least partially spaced apart from the first side of the circular portion, defining at least one chamber therebetween. The chamber has an inlet. An aperture in the at least one first wall defines an outlet of the at least one chamber. At least one second wall extends outwardly from the first side of the circular portion. The at least one second wall has an end portion adjacent to the inlet of the at least one chamber. An internal combustion engine with an electrical generator and a method of cooling an electrical generator are also disclosed.

CROSS-REFERENCE

The present application is a divisional of U.S. patent application Ser.No. 11/849,014, filed Aug. 31, 2007, the entirety of which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a device and method for cooling for anelectrical generator of an engine.

BACKGROUND

Many internal combustion engines include an electrical generator drivenby the engine to generate electrical power. The power generated by thegenerator can be used to power some engine systems (for example, theignition and fuel injection systems), and some systems external to theengine (for example, lights and display gauges of a vehicle powered bythe engine).

A typical generator for an internal combustion engine has a rotorportion and a stator portion. The rotor includes a plurality ofpermanent magnets which generate a magnetic field and the statorincludes one or more wire coils. The rotor is powered by the engine andis thereby caused to spin with respect to the stator. The relativemotion of the magnets and the wire coils induces an electric current inthe wire coils. The current can then be transmitted to the variouselectrical systems that are powered by the generator.

The power output of the generator is typically determined by theinternal structure of the generator, such as the arrangement of themagnets and coils, as well as by the rotational speed of the rotor.Thus, although the power consumption of the various electrical systemsvaries over time, the amount of power produced by the generator at aparticular time cannot be conveniently adjusted to correspond to thevarying levels of power consumption. Thus, the generator is typicallydesigned to always produce sufficient electrical power to meet the needsof the electrical systems under all operating conditions, to ensuretheir continuous operation. When the actual power consumption of theelectrical systems is less than the power produced by the generator, asis usually the case, the excess power is dissipated by the generatorcoils, in the form of heat. Thus, cooling must be provided for thegenerator coils.

One method of cooling the generator coils is to spray them with acoolant, such as oil from the lubrication system of the engine. When thegenerator coils are in contact with the coolant, they will transfer aportion of their heat to the coolant. The coolant is subsequentlytransported to a heat exchanger to dissipate the heat into theenvironment. While this method is effective in cooling the generatorcoils, it suffers from a number of drawbacks. Because the rotor andstator are located in a confined space, and because the rotor isspinning, it is difficult to provide sufficient coolant to adequatelycool the generator coils. In addition, particularly at low speeds, therotation of the rotor does not adequately distribute the coolant withinthe generator to cool every part of the generator coils.

Therefore, there is a need for a way of cooling an electrical generator.

SUMMARY

It is an object of the present invention to ameliorate at least some ofthe inconveniences present in the prior art.

It is also an object of the present invention to cool a stator of anelectrical generator by using a flow of coolant fluid between the rotorand the stator of an electrical generator.

In one aspect, the invention provides a rotor for an electricalgenerator, comprising a rotor body. The rotor body has a circularportion having a first side and a second side opposite the first side,and a cylindrical portion coaxial with the circular portion. Thecylindrical portion extends from the first side of the circular portion.The circular portion and the cylindrical portion define a longitudinalaxis of the rotor body. A plurality of permanent magnets are disposed onthe cylindrical portion. A generally cylindrical recess is defined bythe cylindrical portion and the first side of the circular portion forreceiving a stator. At least one first wall is at least partially spacedapart from the first side of the circular portion. The at least onefirst wall and the first side of the cylindrical portion define at leastin part at least one chamber therebetween. The at least one chamber hasan inlet. An aperture in the at least one first wall defines an outletof the at least one chamber. At least one second wall extends outwardlyfrom the first side of the circular portion. The at least one secondwall has an end portion adjacent to the inlet of the at least onechamber.

In a further aspect, the at least one chamber is a plurality ofchambers. The at least one second wall is a plurality of second walls.

In a further aspect, the at least one chamber is three chambers.

In a further aspect, the end portion of each of the plurality of secondwalls is a first end portion adjacent to a first chamber of theplurality of chambers. Each of the plurality of second walls has asecond end portion adjacent to a second chamber of the plurality ofchambers.

In a further aspect, the inlet of the at least one chamber faces towardthe longitudinal axis.

In a further aspect, at least one third wall is adjacent to the at leastone second wall. The at least one third wall has a portion extendinggenerally parallel to, and spaced apart from, the first side of thecircular portion.

In an additional aspect, the invention provides an internal combustionengine having a crankcase. A crankshaft is disposed in the crankcase. Atleast one cylinder is connected to the crankcase. At least one piston isdisposed in the at least one cylinder and operatively connected to thecrankshaft. A generator is operatively coupled to the crankshaft. Thegenerator comprises a stator fixedly mounted to the internal combustionengine. The stator comprises at least one wire coil. The generatorcomprises a rotor powered by the crankshaft. The rotor comprises a rotorbody. The rotor body has a circular portion and a cylindrical portion.The circular portion has a first side and a second side opposite thefirst side. The cylindrical portion extends from the first side of thecircular portion. The circular portion and the cylindrical portiondefine a longitudinal axis of the rotor body. A plurality of permanentmagnets are disposed on the cylindrical portion. A generally cylindricalrecess is defined by the cylindrical portion and the first side of thecircular portion for receiving the stator. At least one first wall is atleast partially spaced apart from the first side of the circularportion. The at least one first wall and the first side of thecylindrical portion define at least in part a chamber therebetween. Thechamber having an inlet. An aperture in the at least one first walldefines an outlet of the chamber. At least one second wall extendsoutwardly from the first side of the circular portion. The at least onesecond wall has an end portion adjacent to the inlet of the at least onechamber.

In a further aspect, the at least one chamber is a plurality ofchambers, and wherein the at least one second wall is a plurality ofsecond walls.

In a further aspect, the at least one chamber is three chambers.

In a further aspect, the end portion of each of the plurality of secondwalls is a first end portion adjacent to a first chamber of theplurality of chambers. Each of the plurality of second walls has asecond end portion adjacent to a second chamber of the plurality ofchambers.

In a further aspect, the inlet of the at least one chamber faces towardthe longitudinal axis.

In a further aspect, at least one third wall is adjacent to the at leastone second wall. The at least one third wall has a portion extendinggenerally parallel to, and spaced apart from, the first side of thecircular portion.

In a further aspect, the stator further comprises a passage extendingtherethrough. The passage is generally parallel to, and spaced apartfrom, the longitudinal axis of the rotor body.

For the purposes of this application, the terms “radial”, “axial” and“tangential” are defined with respect to the axis of rotation of therotor. Thus, “radial” refers to a direction toward or away from the axisof rotation, “axial” refers to a direction along or parallel to the axisof rotation, and “tangential” refers to a direction perpendicular to theradial direction but not along the axial direction.

Embodiments of the present invention each have at least one of theabove-mentioned objects and/or aspects, but do not necessarily have allof them. It should be understood that some aspects of the presentinvention that have resulted from attempting to attain theabove-mentioned objects may not satisfy these objects and/or may satisfyother objects not specifically recited herein.

Additional and/or alternative features, aspects, and advantages ofembodiments of the present invention will become apparent from thefollowing description, the accompanying drawings, and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, as well as otheraspects and further features thereof, reference is made to the followingdescription which is to be used in conjunction with the accompanyingdrawings, where:

FIG. 1 is a cross-section of an internal combustion engine takenvertically through a longitudinal centerline thereof;

FIG. 2 is a cross-sectional view of an electrical generator andadjoining engine components according to an embodiment of the presentinvention;

FIG. 3 is a perspective view of a catch plate according to a firstembodiment of the present invention;

FIG. 4 is an elevation view of one side of a catch plate according to asecond embodiment of the present invention;

FIG. 5 is a perspective view of the second side of the catch plate ofFIG. 4;

FIG. 6 is a perspective view of a catch plate according to a thirdembodiment of the present invention;

FIG. 7 is a perspective view of a catch plate according to a fourthembodiment of the present invention;

FIG. 8 is an elevation view of a catch plate according to a fifthembodiment of the present invention;

FIG. 9 is an elevation view of a catch plate according to a sixthembodiment of the present invention;

FIG. 10 is a perspective view of the catch plate of FIG. 3, showing anexemplary flow path of coolant; and

FIG. 11 is a schematic cross-sectional view of the electrical generatorof FIG. 2, showing an exemplary flow path of coolant.

DETAILED DESCRIPTION

An electrical generator in accordance with embodiments of the presentinvention will be described with respect to its use in an internalcombustion engine. It should be understood that an internal combustionengine incorporating an electrical generator according to the presentinvention is suitable for use in many different types of vehicles,including snowmobiles, personal watercraft, ATVs, motorcycles andthree-wheeled motorized vehicles. It is contemplated that the presentinvention could also be used in an alternator.

Referring to FIGS. 1 and 2, a four-stroke internal combustion engine 10has three cylinders 12 contained in a cylinder bank 14. Each cylinder 12has a piston 16 associated therewith. Each piston 16 can reciprocatewithin its respective cylinder 12 to change the volume of a combustionchamber 18 associated with the cylinder. Each piston 16 is coupled via acontrol rod 20 to a crankshaft 22 journaled in a crankcase 24, such thatcombustion of fuel (not shown) in the combustion chambers 18 forces thepistons 16 downward to cause rotation of the crankshaft 22. A number ofvalves 28 are provided for each cylinder 12, some of which allow fuel toenter the combustion chambers 18 for combustion therein, and others ofwhich allow exhaust gases (not shown) to exit the combustion chambers 18after combustion has occurred. The opening and closing of the valves 28is controlled by a camshaft 30, which is driven by the crankshaft 22 viaa chain 32. Alternative valve control systems are also contemplated,such as electronically actuated valves. It should be understood that thepresent invention is not limited to the particular engine 10 described,and can be practiced with a variety of other engine types, includingengines with more or fewer cylinders, V-type engines with cylindersarranged in two cylinder banks, two-stroke engines and other variationsthat will be apparent to a person skilled in the art.

The crankshaft 22 is coupled to a rotor 36 of a generator 34. The rotor36 has a rotor body 37 having a number of permanent magnets 40 (bestseen in FIG. 2) mounted thereon, such that rotation of the crankshaft 22causes the rotor 36 to rotate about the axis 42. Referring to FIG. 2,the rotor body 37 is composed of a circular portion 46 that is attachedat its center to the crankshaft 22, and a cylindrical portion 48 onwhich the permanent magnets 40 are mounted. The circular portion 46 andthe cylindrical portion 48 together define a cylindrical recess 49 forreceiving the stator 38, and also define a longitudinal axis coaxialwith the axis of rotation 42. When the engine 10 is in operation, therotation of the crankshaft 22 causes the rotor 36 to rotate about theaxis 42 around the stator 38.

The stator 38, comprising one or more coils of wire 44 (best seen inFIG. 2), is fixed in position inside the cylindrical recess 49, suchthat the rotation of the permanent magnets 40 induces an electricalcurrent in the coils of wire 44. The electrical current is conductedfrom the generator 34 to provide power to one or more systems or devices(not shown) that require electrical power, such as the electricalsystems of the engine 10 and the electrical systems of the vehicle (notshown) in which the engine 10 is used. For example, the engine 10 mayhave one or more of an electrical ignition system, an electrical fuelinjection system or an electronic valve actuation system. The engine 10may be used in a vehicle (not shown) having lights, display gauges or arechargeable battery. It is contemplated that not all of these systemswill be present in a particular engine 10 or vehicle, or that not all ofthese systems will require electrical power in a particular engine 10 orvehicle. For example, the engine 10 may have a carburetor instead of anelectronic fuel injection system, or a fuel injection system drivenmechanically by the engine 10. It is further contemplated that thegenerator 34 may power any other electrical system that forms part ofthe engine 10 or the vehicle in which the engine is used, as needed. Itis further contemplated that the generator 34 could power any othersystem or device that requires electricity.

While the engine 10 is in operation, excess power is generated by thegenerator 34, and this excess power is dissipated as heat in the coils44. In order to reduce the heat build-up in the coils 44, the rotor body37 includes a catch plate 54 to assist in cooling the stator 38, as willbe described in further detail below. Referring to FIG. 2, the catchplate 54 is mounted to the circular portion 46 of the rotor body 37within the cylindrical recess 49. It is contemplated that the catchplate 54 can alternatively be mounted to the circular portion 46 by anyother suitable means, such as welding. It is further contemplated thatthe catch plate 54 may be constructed integrally with the rotor body 37in a one-piece construction.

Referring to FIG. 3, the catch plate 54 will now be described accordingto a first embodiment of the present invention. The catch plate 54 ismade of stamped sheet metal, and has a planar attachment flange 56 witha plurality of holes 58 formed therein, to allow the catch plate 54 tobe mounted to the inside of the circular portion 46 of the rotor body 37using bolts 57, one of which can be seen in FIG. 2. As can be seen inFIGS. 2 and 3, the wall 60 extends away from the plane of the attachmentflange 56, and thus extends away from the circular portion 46 of therotor body 37 when the catch plate 54 is mounted on the rotor body 37.The wall 62 extends radially inwardly from the edge of the wall 60, andgenerally parallel to the circular portion 46 of the rotor body 37 whenthe catch plate 54 is mounted to the rotor body 37. Three walls 70extend radially outwardly from the end portions 74 of the walls 60, andcooperate with the walls 64 and the circular portion 46 of the rotorbody 37 to define three chambers 66. Each chamber has an inlet 67adjacent to the end portions 74 and facing toward the axis 42. It iscontemplated that the catch plate 54 may have more or fewer than threechambers 66 and still be within the scope of the invention. An aperture68 is provided in each wall 64 to serve as an outlet for the chamber 66.It is contemplated that more than one aperture 68 may be provided ineach wall 64. The function of the catch plate 54 to deliver coolant tothe stator 38 will be described in further detail below.

Referring to FIGS. 4 and 5, the catch plate 154 will now be describedaccording to a second embodiment of the present invention. The catchplate 154 is made of welded or cast metal, or moulded plastic, and has aplurality of planar attachment flanges 156. Each attachment flange 156has a hole 158 formed therein, to allow the catch plate 154 to bemounted to the inside of the circular portion 46 of the rotor body 37using bolts 57, one of which can be seen in FIG. 2. As can be seen inFIGS. 4 and 5, the wall 160 extends away from the plane of theattachment flanges 156, and thus also extends away from the circularportion 46 of the rotor body 37 when the catch plate 154 is mounted onthe rotor body 37. The walls 162 and 170 extend radially inwardly fromthe edge of the wall 160 to define a channel 172. Three walls 174 extendradially outwardly from the end portions 176 of the walls 160, andcooperate with the walls 164, 170 to define three chambers 166. Eachchamber 166 has an inlet 167 adjacent to the end portions 176 and facingtoward the axis 42. It is contemplated that the catch plate 154 may havemore or fewer than three chambers 166 and still be within the scope ofthe invention. An aperture 168 is provided in each wall 164 to serve asan outlet for the chamber 166. It is contemplated that more than oneaperture 168 may be provided in each wall 164. The function of the catchplate 154 will be described in further detail below.

Referring to FIG. 6, the catch plate 254 will now be described accordingto a third embodiment of the present invention. The catch plate 254 ismade of stamped sheet metal, and has a planar attachment flange 256 witha plurality of holes 258 formed therein, to allow the catch plate 254 tobe bolted to the inside of the circular portion 46 of the rotor body 37as can be seen in FIG. 2. As can be seen in FIG. 6, the wall 260 extendsaway from the plane of the attachment flange 256, and also extends awayfrom the circular portion 46 of the rotor body 37 when the catch plate254 is mounted on the rotor body 37. Three walls 270 extend radiallyoutwardly from the end portions 274 of the walls 260, and cooperate withthe walls 264 and the circular portion 46 of the rotor body 37 to definethree chambers 266. Each chamber 266 has an inlet 267 adjacent to theend portions 274 and facing toward the axis 42. It is contemplated thatthe catch plate 254 may have more or fewer than three chambers 266 andstill be within the scope of the invention. An aperture 268 is providedin each wall 264 to serve as an outlet for the chamber 266. It iscontemplated that more than one aperture 268 may be provided in eachwall 264. The function of the catch plate 254 will be described infurther detail below.

Referring to FIG. 7, the catch plate 354 will now be described accordingto a fourth embodiment of the present invention. The catch plate 354 ismade of stamped sheet metal, and has a planar attachment flange 356 witha plurality of holes 358 formed therein, to allow the catch plate 354 tobe mounted to the inside of the circular portion 46 of the rotor body 37using bolts 57, one of which can be seen in FIG. 2. As can be seen inFIG. 7, the wall 360 extends away from the plane of the attachmentflange 356, and thus also extends away from the circular portion 46 ofthe rotor body 37 when the catch plate 354 is mounted on the rotor body37. In this embodiment, the wall 360 is composed of a number of straightportions, as opposed to the arcuate walls shown in the embodiments ofFIGS. 3-6. Three walls 370 extend radially outwardly from the endportions 374 of the walls 360, and cooperate with the walls 364 and thecircular portion 46 of the rotor body 37 to define three chambers 366.Each chamber 366 has an inlet 367 adjacent to the end portions 374 andfacing toward the axis 42. It is contemplated that the catch plate 354may have more or fewer than three chambers 366 and still be within thescope of the invention. An aperture 368 is provided in each wall 364 toserve as an outlet for the chamber 366. It is contemplated that morethan one aperture 368 may be provided in each wall 364. The function ofthe catch plate 354 will be described in further detail below.

Referring to FIG. 8, the catch plate 454 will now be described accordingto a fifth embodiment of the present invention. The catch plate 454 ismade of stamped sheet metal, and has a planar attachment flange 456 witha plurality of holes 458 formed therein, to allow the catch plate 454 tobe mounted to the inside of the circular portion 46 of the rotor body 37using bolts 57, one of which can be seen in FIG. 2. The catch plate 454is mounted on the rotor body 37 such that the geometric center 472 ofthe catch plate 454 lies on the axis 42. As can be seen in FIG. 8, thewall 460 extends away from the plane of the attachment flange 456, andthus also extends away from the circular portion 46 of the rotor body 37when the catch plate 454 is mounted on the rotor body 37. Three walls476 extend radially outwardly from the end portions 470 and 474 of thewalls 460, and cooperate with the walls 464 and the circular portion 46of the rotor body 37 to define three chambers 466. In the presentembodiment, the walls 460 between the chambers 466 each have a first endportion 470 at a first distance L1 from the center 472 and a second endportion 474 at a second distance L2 from the center 472. The distance L2is greater than the distance L1. The walls 460 gradually increase indistance from the center 472 between the first end 470 and the secondend 474. This particular shape assists in guiding coolant along theportion of the wall 460 in the direction of the second end portion 474and into the chambers 466 via the inlets 476 when the coolant issubjected to centrifugal force when the catch plate 454 spins in theclockwise direction, as will be described in further detail below. Theinlets 478 are adjacent to the first ends 470 and second ends 474 of thewalls 460 and face toward the axis 42. An aperture 468 is provided ineach wall 464 to serve as an outlet for the chamber 466. It iscontemplated that more than one aperture 468 may be provided in eachwall 464. The function of the catch plate 454 will be described infurther detail below.

Referring to FIG. 9, the catch plate 554 will now be described accordingto a sixth embodiment of the present invention. The catch plate 554 ismade of stamped sheet metal, and has a planar attachment flange 556 witha plurality of holes 558 formed therein, to allow the catch plate 554 tobe mounted to the inside of the circular portion 46 of the rotor body 37using bolts 57, one of which can be seen in FIG. 2. As can be seen inFIG. 9, the wall 560 extends away from the plane of the attachmentflange 56, and also extends away from the circular portion 46 of therotor body 37 when the catch plate 554 is mounted on the rotor body 37.Four walls 576 cooperate with the walls 564 and the circular portion 46of the rotor body 37 to define four chambers 566. In the presentembodiment, the inlets 578 of the chambers 566 are oriented generallytangentially and not oriented toward the geometric center 572 of thecatch plate 554. An aperture 568 is provided in each wall 564. In thepresent embodiment, the portions of the wall 560 between the chambers566 have a first end 570 at a first distance L3 from the center 572 anda second end 574 at a second distance L4 from the center 572. Thedistance L4 is greater than the distance L3. The walls 560 graduallyincrease in distance from the center 572 between the first end portion570 and the second end portion 574. This particular shape assists inguiding coolant along the portion of the wall 560 from the first end 570toward the second end 574 when the coolant is subjected to centrifugalforce, as will be described in further detail below. This facilitatesthe collection of coolant in the chamber 566 adjacent the second endportion 574 when the catch plate 554 spins in the counterclockwisedirection, as will be described in further detail below. An aperture 568is provided in each wall 564 to serve as an outlet for the chamber 566.It is contemplated that more than one aperture 568 may be provided ineach wall 564. The function of the catch plate 554 will be described infurther detail below.

The operation of the catch plate 54 to distribute coolant 600 to thestator 38 will now be described, with reference to FIGS. 10 and 11. Itshould be understood that the catch plates 154, 254, 354, 454 and 554all operate in a similar manner, and the operation of these embodimentswill not be discussed in detail.

Referring to FIG. 11, coolant 600 is delivered to the generator 34 viathe passageway 50. The coolant 600 may be supplied to the passageway 50from the cooling or lubrication system of the engine 10. After thecoolant 600 exits the passageway 50, it passes through the stator viathe passageway 52. Upon exiting the passageway 52, the coolant 600reaches the inside face of the circular portion 46 of the rotor body 37,at a point 602 radially outward of the axis of rotation 42 and radiallyinward of the wall 60.

Referring now to FIGS. 10 and 11, due to the rotational motion of therotor 36 about the axis 42, the coolant 600 is subjected to acentrifugal force once it contacts the rotor 36 at the point 602. Thecentrifugal force urges the coolant 600 generally radially outwardlyfrom the geometric center 72 of the catch plate 54, which is located onthe axis 42. Referring to FIG. 10, the coolant 600 flows from the point602 to a point 604 situated along the walls 60 and 62. Because thechamber 66 is disposed radially outwardly of the wall 60, thecentrifugal force, in combination with the rotational motion of therotor 36, cause the coolant 600 to flow along the walls 60 and 62, andfurther radially outwardly to collect in the chamber 66. In the case ofa catch plate 54 having more than one chamber 66, the coolant 600 willflow into all of the chambers 66 as the catch plate 54 rotates.Referring to FIG. 11, the coolant 600 may instead flow radiallyoutwardly from the point 602 directly into the chamber 66, without firstflowing along the walls 60 and 62, if the rotational position of thecatch plate 54 is such that the axis 42, the point 602 and the chamber66 are aligned.

Referring to FIGS. 10 and 11, the functioning of the chambers 66 willnow be described. Each of the chambers 66 functions in the same way, andonly one chamber 66 will be described in detail. As coolant 600continues to be delivered to the rotor 36 via the passageways 50 and 52,more coolant 600 enters the chamber 66 via the inlet 67. Referring toFIG. 11, this causes the coolant 600 already inside the chamber 66 to beexpelled from the chamber 66 via the aperture 68 in the wall 64, in aspray 606 directed generally toward the stator 38. As the rotor 36continues to rotate about the axis 42, the spray 606 distributes thecoolant 600 evenly over the surface of the stator 38.

When the coolant 600 is in contact with the stator 38, the coolant 600absorbs heat from the stator 38, thereby cooling the stator 38. Thecoolant 600 may then flow by the force of gravity to the bottom of thechamber in which the generator 34 is located, where the coolant 600 canbe collected and circulated through a heat exchanger (not shown) todissipate heat into the environment. The coolant 600 may then bereturned to the passageway 50 to further cool the stator 38.

In one embodiment, the coolant 600 is oil. In this embodiment, thepassageway 50 is supplied with oil 600 by the oil pump (not shown) ofthe engine 10. When the heated oil 600 is collected from the generator34, it may be circulated through a heat exchanger (not shown), andreturned to the oil tank 608 of the engine 10, or any suitable part ofthe oil circulation system of the engine 10. It is contemplated that theoil 600 collected from the generator 34 may instead be returned directlyto the oil tank 608, without passing first through the heat exchanger.The oil 600 is then recirculated by the oil pump to the passageway 50,as well as to other parts of the engine 10.

Modifications and improvements to the above-described embodiments of thepresent invention may become apparent to those skilled in the art. Theforegoing description is intended to be exemplary rather than limiting.The scope of the present invention is therefore intended to be limitedsolely by the scope of the appended claims.

What is claimed is:
 1. A rotor for an electrical generator, comprising:a rotor body, the rotor body having: a circular portion having a firstside and a second side opposite the first side; and a cylindricalportion coaxial with the circular portion, the cylindrical portionextending from the first side of the circular portion, the circularportion and the cylindrical portion defining a longitudinal axis of therotor body; a plurality of permanent magnets disposed on the cylindricalportion; a generally cylindrical recess defined by the cylindricalportion and the first side of the circular portion for receiving astator; at least one first wall at least partially spaced apart from thefirst side of the circular portion, the at least one first wall and thefirst side of the cylindrical portion defining at least in part at leastone chamber therebetween, the at least one chamber having an inlet; anaperture in the at least one first wall defining an outlet of the atleast one chamber; and at least one second wall extending outwardly fromthe first side of the circular portion, the at least one second wallhaving an end portion adjacent to the inlet of the at least one chamber.2. The rotor of claim 1, wherein the at least one chamber is a pluralityof chambers, and wherein the at least one second wall is a plurality ofsecond walls.
 3. The rotor of claim 2, wherein the at least one chamberis three chambers.
 4. The rotor of claim 2, wherein the end portion ofeach of the plurality of second walls is a first end portion adjacent toa first chamber of the plurality of chambers, and wherein each of theplurality of second walls has a second end portion adjacent to a secondchamber of the plurality of chambers.
 5. The rotor of claim 1, whereinthe inlet of the at least one chamber faces toward the longitudinalaxis.
 6. The rotor of claim 1, further comprising at least one thirdwall adjacent to the at least one second wall, the at least one thirdwall having a portion extending generally parallel to, and spaced apartfrom, the first side of the circular portion.
 7. An internal combustionengine, comprising: a crankcase; a crankshaft disposed in the crankcase;at least one cylinder connected to the crankcase; at least one pistondisposed in the at least one cylinder and operatively connected to thecrankshaft; a generator operatively coupled to the crankshaft, thegenerator comprising: a stator fixedly mounted to the internalcombustion engine, the stator comprising at least one wire coil; and arotor powered by the crankshaft, the rotor comprising: a rotor body, therotor body having a circular portion and a cylindrical portion, thecircular portion having a first side and a second side opposite thefirst side, the cylindrical portion extending from the first side of thecircular portion, the circular portion and the cylindrical portiondefining a longitudinal axis of the rotor body; a plurality of permanentmagnets disposed on the cylindrical portion; a generally cylindricalrecess defined by the cylindrical portion and the first side of thecircular portion for receiving the stator; at least one first wall atleast partially spaced apart from the first side of the circularportion, the at least one first wall and the first side of thecylindrical portion defining at least in part a chamber therebetween,the chamber having an inlet; an aperture in the at least one first walldefining an outlet of the chamber; and at least one second wallextending outwardly from the first side of the circular portion, the atleast one second wall having an end portion adjacent to the inlet of theat least one chamber.
 8. The internal combustion engine of claim 7,wherein the at least one chamber is a plurality of chambers, and whereinthe at least one second wall is a plurality of second walls.
 9. Theinternal combustion engine of claim 8, wherein the at least one chamberis three chambers.
 10. The internal combustion engine of claim 8,wherein the end portion of each of the plurality of second walls is afirst end portion adjacent to a first chamber of the plurality ofchambers, and wherein each of the plurality of second walls has a secondend portion adjacent to a second chamber of the plurality of chambers.11. The internal combustion engine of claim 7, wherein the inlet of theat least one chamber faces toward the longitudinal axis.
 12. Theinternal combustion engine of claim 7, further comprising at least onethird wall adjacent to the at least one second wall, the at least onethird wall having a portion extending generally parallel to, and spacedapart from, the first side of the circular portion.
 13. The internalcombustion engine of claim 7, the stator further comprising a passageextending therethrough, the passage being generally parallel to, andspaced apart from, the longitudinal axis of the rotor body.